1. Technical Field
The present invention relates to driving methods for liquid crystal devices, liquid crystal devices, and electronic devices that include such liquid crystal devices.
2. Related Art
A liquid crystal device includes a liquid crystal panel in which a liquid crystal layer is interposed between two substrates. When light is incident on such a liquid crystal device, a liquid crystal material, an orientation layer, and so on that configure the liquid crystal panel react photochemically with the incident light, and ionic impurities are sometimes produced by the reaction. It is furthermore known that ionic impurities diffuse into the liquid crystal layer from sealants, sealing members, and so on during the production of such a liquid crystal panel. In particular, the luminous density of the incident light is higher in a liquid crystal device such as an optical modulation unit (a light valve) that is used in a projection-type display apparatus (a projector) than in a direct-view liquid crystal device, and it is thus necessary to suppress the influence that ionic impurities have on the display.
As a technique for suppressing the influence of ionic impurities on a display, JP-A-2008-58497, for example, discloses a driving method for a liquid crystal display device in which peripheral electrodes configured of a plurality of adjacent electrodes are provided in a peripheral region surrounding a pixel region in at least one substrate in a pair of substrates between which a liquid crystal layer is interposed, and voltage values of driving voltages applied between adjacent electrodes in the peripheral electrodes vary.
According to the driving method for a liquid crystal display device disclosed in JP-A-2008-58497, a horizontal electrical field is produced between adjacent electrodes in the peripheral electrodes, which produces a force that causes ionic impurities to move in addition to a flow produced by minute amounts of sway in the liquid crystals; as a result, ionic impurities that move from the pixel region can be quickly moved outside of the pixel region, and display problems caused by the ionic impurities, such as burn-in, can be prevented.
However, according to the liquid crystal display device and the driving method thereof disclosed in the aforementioned JP-A-2008-58497, the direction of an electric flux line produced by applying an AC voltage between adjacent electrodes A and B in the peripheral electrodes include a direction from the electrode A, which is closer to the pixel region, toward the electrode B, as well as a direction from the electrode B, which is farther from the pixel region, toward the electrode A. Ionic impurities have a positive or a negative polarity, and as such it is possible to pull the ionic impurities using the electrical field produced between the adjacent electrodes A and B; however, it cannot be said that the effect of sweeping off the ionic impurities from the pixel region to the outside thereof is consistently sufficient. There has thus been a problem that the influence ionic impurities contained in the liquid crystal layer have on the display cannot necessarily be sufficiently suppressed.